This is partly due to the puzzles. The puzzles in LoG are many and beautifully varied. And they always give you some kind of clue, even if very subtle, as to how to solve them. Many of the puzzles in the old school crawlers were simply luck-driven without any way to think them through. You just had to do the right thing or carry the right item without any kind of riddle attached to it. All the LoG puzzles let you solve them with your brain instead of dumb luck.
Except for one where you needed a particular item to get into a particular place ...
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Fighter's Challenge
I didn't solve everything, but I got really close. One Iron Door eludes me. And I never found a couple nice items that I know to exist. That means I'll just have to play it again.